Method of coating sheets



2 Sheets-Sheet l Oct. 30, 1945. F. E. FAIRLEY ETAL METHOD OF COATINGSHEETS Filed Fel?. 2, 1943 /ZD/VA/ CZ Patented Oct. 3 0, 1945 2,888,131METHOD OF/COATING SHEETS Frank E. Fairley, Birgiilghdambhois 'l'.lindquist, Bessemer, an y e cliaels and Boilers, Birming Howard C.

ham, Ala., aneignors to Tennessee Coal, Iron and Company, Birmingham,Ala.. a corporation of Ala- Application February 2, 1943, Serial No.474,460

ZCiaims.

The present invention relates to improvements in methods of coatingsheets, and in its broadest aspects aims to provide for effectivelytransferring heat from the molten coating metal to the body of oilfloating on top of the metal so as to maintain the oil body in theoptimum operating condition.

. metal sheet through a molten bath of the coating metal, then upwardlyout of the bath through a body of palm oil. In the normal operation ofsuch methods, difficulties are frequently caused directly or indirectlyby non-,uniformity of the oil temperature. The present invention aims toovercome the shortcomings of theI prior practice by the provision of amethod of transferring small quantities of the molten metal upwardlyinto the region of the .upper zone of the oil body and to permit suchhot molten metal to descend through the oil body and thereby give upheat thereto. In this way the oil body is maintained at the optimumoperating temperature and condition, due in part to the rapid heatexchange and in part to the gentle turbulence set up by the descendingcascade of molten metal through the oil body.

By way of example, apparatus suitable for the practice of the method isshown in the accompanying drawings, inwhich: l

Figure 1 is a vertical longitudinal section through the apparatus.

Figure 2 is a transverse section on line lI-lI thereof.

Referring in detail to the drawings, I represents the wall structure ofa suitable heating chamber supporting the melting pot I2 the con- -tentsof which are adapted to be heated chiey by a burner I4 supplied withgases or other suitable fuel under control of the valve I 6. There is anintermediate wall is approximately in line with the transverse divisionwall 2li of the melting pot. As distinguished from prior practice, theportion of the melting pot to the exit side of the division wall is notdirectly heated by fire, since the chamber 22 below the exit half of thepot is blanked oil' by the wall I8.

Located on the exit side of the division wall .2l there are a pluralityof conventional pairs of exit rolls 24, 2l, and 2l driven by the gears30, I2 and 14. The apparatus is also equipped with a pair ofconventional feed-in rolls 38 which feed the plate P to be coated withmolten metal through flux contained vin a box 3l, thence downwardlythrough the metal bath 4l which may be regarded either as terne metal 0rmolten tin. A pair of feed rolls 42 driven in any suitable'manner forcethe plate through a conventional guide or apron 44 which directs theplate to the lower set of exit rolls 24.

'Ihe top level of the bath of .molten metal at the inlet side of thedivision plate 2l is indicated at 46. The metal level at the right exitside of l 1e division plate 2li is slightly lower, as indicated at 48.Superposed on the metal bath above the metal level 48 on the exit sideof the melting pot is a body of palm oil indicated at 50. through whichthe outgoing sheets are compelled to pass as they leave the pot. 1

The chief feature of novelty of the present invention resides inelevating the molten metal to a point above the normal top metal level48 into the upper region of the body of oil 50, and permitting it tofall by gravity or cascade through the oil body to thus raise itstemperature and create a mild degree of turbulence or agitation. Thismaintains the optimum temperature and condition of the oil body. In theembodiment of the invention illustrated, we provide upper and lowershafts 52 and 54, the upper shaft can'ying a plurality of sprockets 56immersed in the intermediate or upper region of the oil body, and the 1"lower shaft 54 carrying a plurality of sprockets 58 whose lower portionsextend into the molten metal bath. Conveyor chains 60, each carrying aplurality of buckets 62 are trained around the sprockets 56 and 58, andsuitable means are provided for driving the conveyor. In the machineillustrated,.the upper shaft 52 carries a gear 64 which meshes with thegear l2 carried by .one of the exit rolls 26. ever, that the conveyormay be driven independently of the exit rolls, if desired, by a separatemotor drive, so that the bucket conveyor for lifting the molten metaland dropping it through the oil body can be driven at times when it isnot possible to run the exit rolls. Thus the condition of the oil bathcan be maintained, even though temporary shut-downs are necessary tomake repairs or adjustments in the coating apparatus.

In the normal operation of the method, it will be readily understoodthat the sheet to be coated is fed downwardly by the feed rolls 36through It is to be understood, how? 2 l assaisi the nux in the box iland into the molten bath 40. then via feed rolls l2 and exit rolls 24,20 and 28 the sheet is fed upwardly and out to a suitable dischargepoint, and while being discharged is passed through the body oi' palmoil l0, which oil is e'ectively maintained at a proper temperaturewithout the application of direct heat to the metal pot in the zone ofthe oil body, the heat y transfer being effected by the cascading eitectoi l t the molten metal through the oil body. which is a very eillcientmanner oi' effecting a rapid transfer of heat uniformly through allregions of the oil body. The improved method disclosed will improve overprior practice because it will lessen the tendency o! the oil to breakdown,and the useful life of a given batch of oil will be longer. Thusthere will be a marked economy in oil consmnption. Coupled with thiseconomic advantage, the lack o! oil troubles will increase production,and the absence of direct iiring under the oil body will lessen thedanger from nres and will also cut down the fuel cost. Practiceindicates that the invention contributes longer life to the melting pot.This makes for lower maintenance costs. Because of the maintenance olfthe oil body at optimum temperature and condition,V a better coatedmetal product of more uniform quality is produced, and experienceteaches that theproduction of seconds known to those skilledin the artas menders and waste waste, is materially reduced. t

The apparatus herein illustrated is claimed in a division of thisapplication, Serial No. 591,508, tiled May 2, 1945. While the inventionis peculiarly well suited for the coating of ferrous metal sheets orplates with terne metal, it is to be understood that the improved methodis also applicable to the coating of sheets or plates with tin. Variousmodifications may be made by those skilled in the art without departurefrom the invention as defined in the appended claims'.

We claim:

1. In the production of metal coated sheets involving passing each sheetthrough a bath of molten coating metal and then through a body of oilsuperposed on said bath, the improved method comprising elevating someof the molten metal above the top level of the bath in a path in spacedrelation to the path o! movement of the sheet, and emptying the thuselevated metal into the upper portion of the oil body and allowing it tocascade by gravity therethrough so as to maintain the oil at the optimumoperating temperature.

2. In the production of metal coated sheets involving passing each sheetthrough a bath of molten coating metal and then through a body of oilsuperposed on said bath. the improved method comprising sequentiallyelevating separate quantities oi the molten metal above the top level ofthe bath in a path in spaced relation to the path of 'movement of thesheet, and dumping the thus elevated metal and allowing it to cascade bygravity through the oil body so as to maintain the oil at the optimumoperating temperature.

FRANK E. FAIRLEY. LOUIS '1'. LnIDQUIGT. CLYDE .D. MICHAELB. HOWARD C.RODGERB.

